Conventional vehicle steering technology of the type employs so-called steer-by-wire control, and the steering wheel and the steered wheels are connected by a clutch. In the normal condition, however, the steering wheel and the steered wheels are mechanically separated by releasing the clutch, and steering is carried out by driving an actuator connected to the steered wheels by detecting the steering manually exercised by the driver. A backup system is provided to engage the clutch and secure manual steering by mechanically connecting the steering wheel and the steered wheels.
However, in the prior art, the backup system operates only during a failed condition, and therefore steer-by-wire control may be initiated even when the backup system is in an abnormal condition. Consequently, the backup system cannot be guaranteed to operate in the failed condition.